Kiev had been worried that the convoy was a ruse to resupply the separatists or a pretext for a Russian invasion.

A Ukrainian military spokesman tells Reuters that 184 vehicles were confirmed to have left Luhansk so far. Asked how many Russian vehicles still remained in Ukraine, he replied: "I don't know."

However, in a foreign ministry statement, Moscow said: "We confirm our intention to continue cooperation with the ICRC in attempts to provide humanitarian aid to the people of south-eastern Ukraine."

In a separate development, Reuters quotes NATO as saying the alliance has mounting evidence that Russian troops are operating inside Ukraine and launching artillery attacks from Ukrainian soil, an accusation rejected by Russia.

But Russia's United Nations Ambassador Vitaly Churkin, speaking at a Security Council session, accused Western powers of not being concerned "about the fact hundreds of civilians are dying."